import time

def main():
    # 一次性读取整个文件内容
    with open('test.txt','r',encoding='utf-8') as f:
        print(f.read())
    # 通过for-in循环逐行读取
    with open('test.txt',mode='r') as f:
        for line in f:
            print(line,end='')
            time.sleep(0.5)
    print()

    #读取文件按行读取到列表中
    with open('test.txt') as f:
        lines = f.readlines()
    print(lines)

if __name__=='__main__':
    main()